This invention relates to a ribbon forwarding apparatus of impact type printer for printing on a recording paper wound on a platen by moving printing means disposed at a specified position on a carrier which moves along this platen to a printing position, and striking it through an ink ribbon at the printing position.
Conventionally, as a ribbon forwarding apparatus of impact type printer of this sort, for example, the structure as shown in FIG. 3 was known. This ribbon forwarding apparatus is elevatably mounted on a carrier which possesses a printing unit and moves along a platen, a ratchet wheel 22 threaded in pitch C corresponding to the feed rate of the ink ribbon is pivoted on a lower face 21 of an elevation table having an ink ribbon cartridge and a correction ribbon cartridge mounted in its upper and lower faces, and there are a feed pawl 23 which is engaged with this ratchet wheel and a slider 24 which is reciprocally moved in the direction of arrow A in synchronism with the printing speed by drive means (not shown), in which the ratchet wheel 22 is rotated in the direction of arrow B by one pitch each, that 1, .theta.c.degree., by the reciprocal motion of the slider 24 so as to forward the ink ribbon intermittently when printing. When erasing, on the other hand, the elevation table ascends to position the correction tape at the printing unit, and as the printing unit strikes the recording paper on the platen by way of this correction tape, the ink on the recording paper is picked up by the correction tape and is erased.
In this erasing action, it is not always necessary to forward the ink ribbon, but if the tape forwarding is null, when continuously erasing multiple letters, the ribbon may be loosened by vibrations to stick to the daisy wheel, or perfect transfer of the ink into the recording medium may not be achieved when printing.
However, in said conventional ribbon forwarding apparatus, although forwarding of ink ribbon in erasing action is enough by a small amount necessary for preventing its looseness, the ink ribbon was actually forwarded in the erasing action by the same amount of the feed of the ink ribbon in printing action, the ink ribbon was wasted by the purposeless forwarding more than necessary for prevention of the loosening of the ribbon in erasing action.